Moisture Content Calculator

Moisture content is the mass of water in a sample expressed as a percentage. The reference method is the oven-dry test: weigh the wet sample, dry it at about 105°C until its weight stops changing, weigh it again, and compute (wet weight − dry weight) ÷ dry weight × 100. This gives moisture content on a dry basis. Handheld meters estimate the same value through proxies such as electrical resistance, but the oven test is the standard against which everything is compared.

This is the #1 source of confusion. Dry-basis moisture (MC_db) = (wet − dry) ÷ dry × 100; wet-basis moisture (MC_wb) = (wet − dry) ÷ wet × 100. A sample weighing 120 g wet and 100 g dry contains 20 g of water, so MC_db = 20 ÷ 100 × 100 = 20%, while MC_wb = 20 ÷ 120 × 100 = 16.67%. Same sample, two correct-looking numbers — so always state which basis you are using.

Follow your industry's convention. Wood, lumber, and soil science use dry basis — this is why green wood can legitimately be quoted at 60–200% moisture, which is impossible on a wet basis. Grain, food, and compost use wet basis: market corn is 15.5% wet basis, and compost is 40–65% wet basis. If someone just says "20% moisture" without a basis, the number is meaningless.

Yes, on a dry basis — and it is completely normal. Because dry basis divides by the dry weight only, water can outweigh the solids: a wet sample of 180 g with 100 g of dry matter is 80 ÷ 100 × 100 = 80% moisture dry basis (44.44% wet basis). Fresh-sawn lumber commonly tests at 60–200% dry basis. Wet-basis moisture can never reach 100% because the water mass is always a fraction of the total wet mass.

Use MC_wb = MC_db ÷ (100 + MC_db) × 100. For example, 20% dry basis → 20 ÷ 120 × 100 = 16.67% wet basis; 100% dry basis → 100 ÷ 200 × 100 = 50% wet basis. The result is always lower than the dry-basis number because wet basis divides by the larger wet weight.

Use MC_db = MC_wb ÷ (100 − MC_wb) × 100. For example, 25% wet basis → 25 ÷ 75 × 100 = 33.33% dry basis; 50% wet basis → 50 ÷ 50 × 100 = 100% dry basis. The dry-basis result is always higher, and it grows very fast as wet basis approaches 100%.

Typical ranges, all dry basis: fresh-sawn lumber 60–200% (well above the fiber saturation point of about 28–30%, the moisture level below which wood starts to shrink); air-dried lumber about 13–17%; kiln-dried lumber for interior furniture and flooring 6–8%; seasoned firewood roughly 15–25%. Firewood above about 25–30% burns poorly and loses heat boiling off water.

Grain and food are quoted wet basis: corn 15.5% and wheat 13.5% are the standard delivery/moisture-shrink references, soybeans 13.0%, rice 14.0%. All-purpose flour is about 12–14%, green coffee beans about 10–12%, honey at most 18.6% by US standard, and fresh fruit and vegetables run about 75–95%. Compost is held at 40–65% wet basis to keep microbes active without going anaerobic.

Soil moisture is reported gravimetrically (dry basis) from the oven test: for a medium-textured loam, field capacity — the water left a day or two after soaking — is about 29% and the permanent wilting point, below which plants cannot extract water, is about 13%. Sandy soils hold far less (roughly 5–12% at field capacity) and clays hold far more (roughly 30–42%). Sensors in the field report volumetric water content instead, which is gravimetric × bulk density.

Pin meters estimate moisture from electrical resistance between two pins, and they are calibrated for specific wood species and only reliable below the fiber saturation point (about 28–30%); above it they read low. Temperature, species setting, surface wetness, and pin depth all shift readings. The oven-dry test physically removes and weighs the water, so when precision matters — sales, grading, research — the oven test is the referee and meters are quick checks, not substitutes.